Fish injuries resulting from transient operating conditions in a Brazilian hydropower plant: morphological, physiological and biochemical evaluation in Pimelodus maculatus (Siluriformes: Pimelodidae)

Abstract This study investigated injuries sustained by Pimelodus maculatus caused by transient operating conditions in a Brazilian hydroelectric power plant. Fish (n = 43) that inhabited the tailrace and appeared on the water surface after changes in the operating conditions were evaluated (IF). Additionally, fish (n = 10) captured using longline in the vicinity of the tailrace were used for comparisons (NF). Blood samples were evaluated for cortisol, glucose, and lactate concentrations. Tissue samples (gill, liver, brain, and muscle) were analyzed for oxidative stress biomarkers (TBARS, protein carbonyl content, and catalase activity) and histology (gill, liver, and spleen). The most prominent findings in IF were barotraumas with intra-abdominal hemorrhage and swim bladder rupture. Cortisol and glucose concentrations were lower for IF when compared to NF. IF also suffered from oxidative stress, as indicated by increased TBARS in the liver and brain, as well as increased protein carbonyl content in the gills and liver. The main histological alterations induced by the adverse conditions were circulatory disorders, such as telangiectasia and gill aneurysm, hepatic congested veins, and hemorrhage in the liver and spleen. The abrupt drop of pressure resulting from changes in the operating conditions of the turbines caused barotraumas and oxidative stress, which were the leading causes of fish mortality